This invention generally relates to control systems, and more particularly to the architecture of a control system for controlling material handling operations.
Automated material handling systems are available in a wide variety of forms, such as conveyor systems, automatic guided vehicles, electrified monorails, automatic storage and retrieval systems, and others. In the past, these types of material handling systems have been controlled by control systems having generally one of two different types of architecture. In one architecture, each of the sensors and actuators in the system is directly connected to a central controller. For example, in a conveyor system, the motor controllers that control the conveyors, along with the photo eyes that sense articles being carried on the conveyor, would all have direct wire connections to the central controller. In a second type of control architecture, a central controller is directly connected to each and every actuator or sensor in the material handling system via a network or other type of system that uses shared communication channels. While this latter type of system has the advantage over the former system in that it reduces the wiring necessary to implement the system, both systems have their drawbacks. In particular, both systems require the central controller to deal with each and every actuator and sensor in the system. This may severely tax the capabilities of the central controller, requiring it to prioritize messages and delay certain responses. Additionally, such systems may be difficult to scale to different sizes when implemented. For example, a central controller that can accommodate 10 inputs and outputs may not be capable of accommodating 100 or even 1000 inputs and outputs without redesigning the entire central controller. Past systems that have used shared communication channels have also required high bandwidths in order to accommodate all the necessary communication.
Accordingly, the desirability of a material handling control system that overcomes these and other disadvantages can be seen.